Back to 10,000 B.C.

Life in North America was rough in 10,000 B.C. The great reptiles were long gone, but giant mammals took their place, roaming the countryside where “paleo-Indians” hunted and gathered. There were sloths the size of cars, bears twice as big as grizzlies, four hundred pound saber tooth cats and the Columbian mammoth, an elephantine behemoth dwarfing the pachyderms of the present day.

And then came catastrophic global climate change, triggering a second Ice Age that sent glaciers down the continent as far as the southern tip of Lake Michigan.

The History Channel’s “Journey to 10,000 BC,” out now on DVD, tries to imagine those years as it was experienced by the scattered bands of humans inhabiting the continent. The computer-generated animation representing prehistoric times is garish and goofy. What’s interesting are the interviews with archeologists, geologists and other scientists sifting through the sand for spearheads and bones. The result is an often-vivid sense of what life may have been like in the primeval New World.

Piecing together history is often a lot like detective work and puzzling out pre-history can amount to a cold case with few clues. As a result, the most conflicting theories can find adherence. “Journey to 10,000 BC” steps gingerly among several of them, including archeological evidence suggesting that many Native Americans may have been of European rather than Asian origin and that a meteorite striking the glaciers may have set off a second Ice Age and the mass extinction of many animal species as well as the temporary retreat of humanity.